Prescribing submaximal training based on the lactate threshold improved aerobic fitness in dogs with preclinical myxomatous mitral valve disease

Abstract Exercise intolerance may be a primary symptom of myxomatous mitral valve disease (MMVD) and a significant factor in reducing the quality of a dog’s life. Aerobic training effectively improves oxygen uptake and life expectancy in human patients with chronic heart failure. Lactate threshold (LT) is used to prescribe training programs. We conducted a study with dogs diagnosed with asymptomatic MMVD (stage B1), using the velocity corresponding to the visual lactate threshold (VLTv) and an eight-week submaximal training program (STP), three times a week, with each session lasting 30 min, to improve their aerobic fitness. The dogs were assigned into two groups: a healthy control group and a MMVD group (stage B1). The treadmill-based graded exercise test (GXT) was used to determine the lactate-velocity curve (LVC) inflexion point. We utilised the velocity corresponding to 70% VLTv as the external load STP, representing a training zone between 145 and 157 bpm. Before the STP, VLTv and maximum velocity (Vmax) were lower in B1 dogs compared with the healthy group. The VLTv increased in the B1 dogs, resulting in rightward shifts of the LVC. The VLT values for healthy dogs were 3.62 ± 0.90 m/s and 4.75 ± 0.6 m/s; for B1 dogs were 3.03 ± 0.6 m/s and 3.8 ± 0.75 m/s in the pre-STP and post-STP. The Vmax values were 4.50 ± 0.70 m/s and 4.75 ± 1.04 m/s for healthy dogs, and 4.0 ± 0.53 m/s and 4.66 ± 0.74 m/s for B1 dogs. In both groups, changes in the relationship between lactatemia and exercise work may indicate improvements in aerobic and anaerobic capacities. VLTv, as an external training loading, should be considered when prescribing tailored training programs for dogs with asymptomatic myxomatous mitral valve disease to improve their muscular and cardiovascular function and exercise tolerance.